This invention relates to a device for infusing a therapeutic agent to a desired site within a patient or withdrawing a fluid from a patient, and more particularly, to such a device which is implanted such that no portion is transcutaneous. Its access portion is subcutaneous but designed so as to facilitate repeated access by the percutaneous route.
In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an infusion device for intravenous drug infusion, multiple vein punctures over a lengthy period results in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an infusion system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent into an artery for diagnostic purposes. In certain conditions, there is a need to remove a body fluid repetitively for analysis from a remote body site. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and small diameter optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or removing body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements by patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and are a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir which can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an outflow catheter which communicates with a vein or other site within the patient where it is desired to infuse therapeutic agents. Implantation of such devices generally proceeds by making a small subcutaneous pocket in the patient under local anesthesia. The internal outflow catheter is tunneled to the desired infusion site. When the physician desires to infuse or remove material through the port, a syringe is used with a hypodermic needle which pierces the skin over the infusion port and through the port septum and into the reservoir.
Although presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing, there are limitations in the diameter of needles which can be used to penetrate the septum, since large diameter needles can seriously damage the septum. These diameter limitations severely restrict the flow rate of fluids passing through the port. In cases where it is desirable to infuse drugs using a flexible external inflow catheter, the catheter must be fed through the needle which penetrates the septum. Such catheters have an extremely small inside diameter and, therefore, impose severe limitations on fluid flow rate.
Presently available implantable drug infusion devices must also have a significant size to provide an acceptable target surface area for the physician who must locate the port and penetrate the septum properly with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within them or in the implanted outflow catheter, since it is difficult if not impossible to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal outflow catheter. Present infusion ports have a retained volume beneath the self sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a physician desired to deliver drugs to the same infusion site which are incompatible when mixed. In addition when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports comprises an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the physician attempting to pierce the port septum will not properly enter it, leading to the possibility of bending or breaking the hypodermic needle.
The present invention relates to various forms of implantable infusion ports which provide numerous enhancements over prior art devices. In accordance with one aspect of the present invention, the infusion port incorporates a funnel shaped entrance orifice which communicates with a reduced diameter exit orifice. An articulating catheter valve is positioned in the infusion port housing between the inlet and outlet orifices which replaces the compressed rubber septum of conventional infusion ports. Various forms of catheter valves can be employed. One such valve is a leaflet valve having one or more flat disks of the elastomeric material having cuts through them to define leaves or flaps which normally resist the flow of fluids across the valve, but can be penetrated by an introduced catheter or other filament.
The infusion ports of this invention are implanted in the same manner as prior art devices. When the physician desires to infuse a therapeutic agent, remove a body fluid, or have vascular access, a slit wound is formed in the skin overlying the infusion port. An external inflow catheter (or other filament) is then fed into the incision with the aid of a guide wire or obturator and into the entrance orifice of the infusion port. The entrance orifice guides the introduced catheter into a proper "docking" position with the articulating catheter valve. By pushing on the externally introduced filament, it is forced through the catheter valve, thereby providing an open communication pathway for the infusion of therapeutic agents, extraction of body fluids, introduction of an optical fiber, clearing by a wire, etc. The introduced filament can be fed into the outflow catheter to any extent desired. In the case of introducing a flexible catheter a guide wire can be inserted into the external catheter to increase its rigidity. Once inserted, the guide wire obturator is removed and material can be infused through the external catheter. The convenient access to the port and internal outflow catheter enables these elements to be cleared with a clearing wire so that they can always be cleared, avoiding the problem of permanent impaction of prior art devices. In addition, the ability to feed a guide wire into the infusion port and internal catheter of this invention enables the internal catheter to be repositioned using a bent or "steerable" guide wire.
The infusion ports having an articulating catheter valve possess the advantage that they have a very small reservoir or "dead space" meaning that virtually all of the infused fluid is throughput to the desired infusion site. This invention, therefore, facilitates infusion of incompatible materials in a serial fashion since there is very little of the previously infused fluid in the device when a subsequent infusion is carried out. This invention also facilitates simultaneous infusion of incompatible materials by using a multi-lumen catheter.
Another aspect of the present invention is a design for an infusion port which is configured such that a line normal to the plane formed by the entrance orifice is nearly at a right angle to the longitudinal axis of the exit passageway. The port access opening guides an introduced filament toward and into the outflow catheter. This approach of guiding a catheter to undergo a bend through the port can be used with conventional port designs having a self-sealing rubber septum. Other aspects of the present invention relate to providing a reservoir within an infusion port for containing an antimicrobial fluid, offering enhanced protection against introduced infection. This invention is further related to various means of securely fastening an outflow catheter to an infusion port.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings